wilbur



R. S. WILBUR.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED xuma n. 1917.

1,303,001. Patented Mai 6,1919.

/n yew/0r. Ray 3. 1407mm W V MM lit RAY S; WILBUE, 01F JERSEY CITY, NEW JERSEY, AhfiIG-NQR TO WEfiTERN ELECTRXG GQMPANY, INCORPORATED, 0E NEW YOEMK, N. Y., A C(li tlzflltrl'lltll l' 0F llEW TELEPHONE'EXCHANGE Specification of Letters l i-ttcnt.

a 111 alien clay is Application illiid Siunc 11. MP2. Serial li o l'?-il,il5.

To all whom it may concern:

Be it known that I, RAY S. \VILBUR, a citizen of the United States, residing at Jersey City, in the county of Hudson and State of New Jersey, have invented certain new and useful Imprm'ements in Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone ex change systems, and more particularly to an arrangement for controlling the application of signaling current to the lines of called subscribers for the purpose of signaling such subscribers. In existing telephone exchange systems it is common to provide an operators cord circuit with a switching arrangement for the purpose of automatically associating a source of signaling current with the conductors of such cord when such cord has been associated with a called line, by

means of the usual plug and jack. It is also common in such systems to direct the slgnaling current through the windings of a relay.

and out over the called line, through the signal of such line, for the purpose of operating such signal. This relay which is ordinarily referred to as the ringing trip relay is generally of a marginal character and is arranged so that it will operate in the sig naling circuit in response to the operation of the hook switch of the called subscriber, which shunts the signal and reduces the resistance of the signaling circuit. lln utilizing a marginal relay of this character it has been found that the longer the line over which the signaling takes place, the less relative difierence there is in the resistance of the circuit through the marginal relay due to the shunting of the signal, and hence the smaller the margin upon which such relay must be made to operate. Therefore, it has been found by experience that in utilizing the ordinary marginal relay, the length of line to which it can be successfully used is limited. This length of line upon which such relay can be used is relerred to as the tripping range of the relay.

It is an oloject of the present invention to increase the tripping range of the tripping relay.

in accordance with a feature of the present invention, means are provided to maintain the magnetic flux produced by the signaling current in the core of the trip relay,

reversal of the magnetic flux in the core of the tripping relay is prevented and such relay is rendered much more sensitive, thus ncreasing its tripping range. ln the drawmg, in which one embodiment of the invention is illustrated, the figure discloses the calling end of a cord circuit and a subscribers line circuit.

The subscribers line shown to the right is provided with the usual substation a paratus including a signal which may e the usual belll, and a switchhook 2. 'lhe subsoribers line terminates in the central ofiicc in the usual jack 3, and is provided at the central oilice with the usual line relay 4, and the cut-off relay 5. Only the calling end of the cord circuit is shown, and associated therewith is the calling plug 6, the test relay 7, the ringing relay 8, the supervisory relay 9, and the trip relay 10. With the exception of the trip relay all of these relays are of the usual construction. The trip relay 10 is provided with two windings 1.1, and 12, which are, as shown, wound about the common core of the relay in the same direction. These two windings are included in parallel in the signaling circuit, as will presently appear, and are connected through a commutator 13 to a source of alternating signaling current indicated by the plus and minus sign adjacent such commutator.

The invention will be best understood by a description of the signaling operation. llt will be assumed, therefore, that the operator has inserted the plug 6 into the jack 3 of the subscribers line, and that such line is idle. lln response to this operation a circuit is established for the test relay 7, which circuit may be traced from battery, supervisory lllll of relay 7, and thence to ground through the cut-oil relay 5. The energization of the relay 8 in this circuit, establlshes the signaling circuit, which extends from the source of alternating rin 'ng current to the commutator 13, then a ternately through the windings of the tripping relay 10 to the lower armature and upper contact of the relay 8, the ring strand of the cord, the ring of the plug, the ring of the jack, the bell 1, through the condenser, back of the tip of the jack, the tip of the plug, through the tip strand of the cord, upper armature and contact of relay 7, upper armature and lower contact of relay 8 to ground. The alternating current passing over this circuit causes the operation of the hell 1, and for each alternation, as the com-mutator 13 revolves, first the negative half of the wave passes through one of the windings such as 11 of the trip relay 10, followed by the positive half of the wave through the opposite winding 12. As these windings are directed the same way on the core and by virtue of the commutator the waves of opposite polarity are caused to pass through each of the windings in the same direction, the resulting flux in the core of the magnet does. not change in direction.

When the called subscriber responds, the switchhook in closing its contacts shunts the high resistance bell from the ringing circuit. This lowers the resistance of the circuit to such an extent that the trip relay 10 will operate. The operation of the trip relay 1O removes the shunt from around the relay 18,

which relay is immediately energized in se-- rice with the relay .7, and at its armature and contact connects battery to the circuit between the relays 8 and 18, short-circuiting the relay 8. The release of the relay 8 opens the previously traced ringing circuit.

For the sake of simplicity the usual commutator for providing alternate ringing to silent periods in the signaling circuit has been omitted, as it is obvious that such an arrangement could be applied to the system disclosed.

What is claimedis:

1. In a telephone exchange system, a signal responsive to alternating current, a signaling circuit, a source of alternating signaling current, a control relay included in such circuit, and means also included in said signaling circuit for maintaining the flux pro du'ced in the core of said relay by said signaling current, constant in direction.

2. In a telephone exchange system, a signal, a signaling circuit, a double wound control relay, a source of alternating signaling current, and means for alternately switching the windings of such relay into the signal circuit as the polarity of the signaling current changes.

3. In a telephone exchange system, a signal, a signaling circuit, a source of alternating signaling current, a control relay, and a commutating device for reversing the direction of the current through the windings of such control relay as the polarity of the signaling current reverses.

1. In a telephone exchange system, a signal, a signaling current, a control relay provided with windings wound upon the core thereof in opposite directions, a commutating devicefor alternately connecting such win-dings with such source of signaling current as the polarity of such current changes.

5. In a telephone exchange system, a signal responsive to alternating current, a source of alternating signaling current, a control relay included in such circuit, and means for producing unidirectional pulsating magnetizing forces in the core of said relay having twice the frequency of the source of alternating signaling current in said signaling circuit.

In witness whereof, I hereunto subscribe my name this 8th day of June A. D., 19.17.

RAY S. WILBUR. 

